Reciprocating punch and die apparatus with stripper mechanism



R. G. FRIEDMAN 2,705,333 RECIPROCATING PUNCH AND DIE APPARATUS WITH STRIPPER MECHANISM 4 Sheets-Sheet 1 April 5, 1955 Flled Oct 10, 1952 um 5 v A wm Nm mum/j \E. E, Q w m 2 A A Wm mm vm m EMMY 8 V mv h mu Q v IN V EN TOR. P0255137" 6. FR/EzJ/MIV R. G. FRIEDMAN 2,705,333 RECIPROCAT DIE APPARATUS HANISM April 5, 1955 INC PUNCH AND WITH STRIPPER MEC 4 Sheets-Sheet 2 Filed Oct. 10, 1952 INVEN TOR. ROBERT G; PIP/[OMAN BY W R/(HEY 7715, W 7

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April 5, 1955 G. FRIE RECIPROCA TING PUNCH AND DIE APPARATUS WITH STRIPPER MECHANISM 4 Sheets-Sheet 3 Filed Oct. 10, 1952 INVENTOR. ROBERT a FR/EDNA/V Eve/15 WATT-S A T TORA/EYS April 5, 1955 R, G. FRIEDMAN 2,705,333

RECIPROCATING PUNCH AND DIE APPARATUS WITH STRIPPER MECHANISM Filed Oct. 10, 1952 4 Sheets-Sheet 4 INVENTOR.

ROBERT G: FRIED/141V BY R/CHEX WATTS, EDGE Ni-M-IVENMY z Zn? ATTa Y5 United States Patent RECIPROCATING PUNCH AND DIE APPARATUS WITH STRIPPER MECHANISM Robert G. Friedman, Tiflin, Ohio, assignor to The National Machinery Company, Tiflin, Ohio, a corporation of Ohio Application October 10, 1952, Serial No. 314,162 3 Claims. (Cl. -11) This invention relates to machines for making bolts or the like and, more particularly, to a machine for making cap screws having a socket or recess in the head thereof. The present invention is in the nature of an improvement in a stripper apparatus for freeing the socketed head of a cap screw from the punch forming the socket and is similar to the apparatus disclosed and claimed in the co-pending application of John H. Friedman, Serial No. 91,030, filed May 3, 1949, now Patent No. 2,680,860, entitled Apparatus for Forming Hollow Articles.

As pointed out in said co-pending Friedman application it is advantageous to punch the hexagonal socket in the head of the cap screw by apparatus which includes a stationary holding die carried by the header slide which also carries the punch or socketing tool. It is characteristic of punching or socketing operations that, when the head portion of the blank is confined, the metal of the head tends to contract or spring back after the punch has passed a given section of the blank so that at the completion of the socketing stroke the body of the blank strongly grips and contracts about the punch. Accordingly, the blank should be restrained and held in the holding die while the punch is withdrawn. The method and apparatus for carrying out such socketing operations without excessive die wear is accomplished as disclosed in said John H. Friedman application by confining the head only during the punching operation and thereafter relieving the confinement of the head before the punch is withdrawn from the socket 111 the blank.

It is the object of this invention to provide a machine for making socket head cap screws wherein the head portion of the cap screw is confined in a die slidably mounted on a reciprocating header slide while the socket is being punched and wherein the die carries a stripper sleeve surrounding the punch and wherein the punch and sleeve are moved axially with respect to the header slide by movement of the pitman WhlCh drives the header slide.

It is also an object of this invention to provide a machine for making socket head cap screws wherein the header slide is reciprocated by a pitman which is pivoted to the header slide and wherein the punch which forms the socket and the stripper sleeve for the punch are carried by the header slide and are moved axially with respect to the header slide in response to pivotal movement of the pitman with respect to the header slide.

Recent developments in the machines for making socket head cap screws which are also known as Allen-head cap screws have resulted in adoption by the industry of a machine wherein the shank of the cap screw is held in a die while a header slide which carries a head confining die, a stripper and a punch is reciprocated with respect to the blank held in the die breast. To minimize die wear and prolong the life of the tools, the confining die is provided with a recess which is gradually enlarged from the end face of the confining die so as to relieve the side walls of the head during the punching of the hexagonal socket in the head. The resulting taper on the side walls of the head is eliminated in the finished article since the head is drawn through the minimum diameter of the confining die as the header slide recedes. The stripper and punch are moved axially with respect to the confining die so that the blank is held in the holding die of the die breast while the header slide recedes and so that the punch remains in the socket of the head until the head portion of the blank is released with respect to the confining die. The stripper sleeve is also arranged so as to bear against the head of the blank and hold it in the bed frame die while the punch is withdrawn from the socket. According to the present invention the header slide is driven by a pitman pivoted on the header slide at one end and surrounding an eccentric on the crankshaft on the other end. The driving motion of the pitman results in a pivotal swing of the pitman on the header slide and I have provided means whereby the pivotal motion of the pitman may be utilized to move the punch and stripper in timed relation to the movements of the header slide.

Further objects and advantages will appear from the following description and appended drawings, wherein:

Fig. 1 shows the header and stripper mechanism partially in section when the header is in the extreme forward position;

Fig. 2 is a similar view after the blank has been removed fromhthe header die and prior to the withdrawal of the punc Fig. 3 is a similar view in which the stripping operation is complete;

Fig. 4 is an enlarged view in section along 44 of Fig. 1 showing in detail the stripper mechanism;

Fig. 5 is an enlarged view in section along 55 of Fig. 2 showing in detail the stripper mechanism; and

Fig. 6 is an enlarged view in section along 6-6 of Fig. 3 showing in detail the stripper mechanism.

Referring to the drawings, the header slide 10 is mounted in the conventional manner for reciprocation to and from the die block 11. The header slide extension 12 is mounted on the face of the header slide 10 and has a bore as at 13 to receive a die sleeve 14. In the embodiment disclosed, the die sleeve 14 is arranged to permit limited axial motion relative to the header slide extension 12 and is provided with a stop 15 which engages the radial .face 16 of the header slide extension thus limiting the forward axial travel. The header slide extension has an air pressure inlet 17 in communication with the enlarged section 18 which, in conjunction with the rearward surfaces of the die sleeve 14, forms a fluid motor tending to hold the die sleeve in the forward position with the stop 15 in engagement with the wall 16. This particular feature is desirable in con junction with the forging of hollow articles since it insures that the die sleeve surrounds the bolt head before any forging takes place. The forward section of the die sleeve adjacent to the die block 11 has a bore 19 to receive the stripper sleeve 21. The stripper sleeve 21 is axially slidable in the bore 19 of the die sleeve 14 and is formed with an enlarged rearward section 22 which abuts against the surface 23 of the die sleeve thereby limiting the axial travel relative thereto. A punch 24 is axially slidable within the bore of the stripper sleeve 21 and is mounted at its rearward end in a plunger block 26 which is slidable in the enlarged bore 27 of the die sleeve 14. The plunger block 26 is formed with a forward surface 28 which, when engaged with the radial surface 29 of the die sleeve 14, acts as a stop to limit the forward travel of the plunger block 26 and, in turn, limit the forward travel of the punch 24. This mounting of the punch within the plunger block 26 is such that the plunger block limits the forward motion of the punch but does not transmit any of the forward thrust during the forging operation. A second plunger block 31 abuts against the rearward surface of the first plunger block 26 and also the rearward surface of the punch 24 and transmits the forward thrust to the punch during the forging operation itself. A plug member 32 is situated directly behind the second plunger block 31 and abuts on its rearward surface against the wedge 33. During the forging operation the forward thrust is transmitted from the header slide through the wedge 33 to the plug member 32 which, in turn, transmits the force through the second plunger block 31 to the punch 24.

The stripper sleeve 21 is connected to the stripper sleeve advance levers 34 by a series of sliding members which are positioned between said levers and said sleeve and transmit the forward thrust from the levers 34 to the stripper sleeve 21. A second group of sliding members are situated between the second plunger block 31 and the punch advance lever 36 and serve to transmit the forward thrust from this lever 36 to the second plunger block 31 and, in turn, to the punch 24 during the stripping operation.

The series of sliding members between the stripper sleeve and the stripper sleeve advance levers is composed of a plurality of stripper pins 37 spaced around the rearward surface of the stripper sleeve which pass through bores in both plunger blocks and abut against a stripper tube 38 at the other end. These bores in the plunger blocks provide guiding means for the pins but do not restrict their axial movement relative to the plunger blocks. The stripper tube in turn abuts against a plurality of stripper advance pins 39 at its rearward end. The stripper advance pins abut against the stripper sleeve operating levers 34 thus completing the series of sliding members which transmit the thrust from the stripper advance lever to the stripper sleeve.

The second series of sliding members which transmit the thrust from the punch advance lever to the punch is composed of a punch pin 41 which is slidably mounted in the stripper tube 38 and abuts against the second plunger block 31 at its forward end. An advance block 42 is situated between the punch pin 41 and the punch advance lever 36 and is bored to receive the previously described stripper advance pins and provides guide means for said pins but does not restrain their axial movement. The stripper tube and the advance block 42 are slidably retained in a passage through the header slide but are not restricted axially thereby.

The stripper tube 38 and the advance block 42 are so proportioned that if the stripper advance pins do not extend beyond the advance block 42, the block will engage and advance the stripper tube along with the punch pin. This structure insuresthat the punch and the stripper drive are advanced as a unit when desired.

Since the die sleeve 14 is formed with the taper 61 the head of the blank 56 is drawn down to the small diameter of the taper during this phase of the stripping operation. For this reason it is necessary that the stripper assembly be capable of rather large loads.

The advance levers 34 and 36 are pivoted to the header slide as at 43 and are formed with cam surfaces along which the cam follower 44 rolls. The cam follower 44 is pivoted to a toggle mechanism comprising a link 46 and a second link 47. The link 47 is pivoted at one end to the header slide as at 48 and at the other end to the first link 46 as at 49. The link 46 carries the cam follower 44 and is pivoted at the end opposite the cam follower 44 to the pitman 51 as at 52. The pitman 51 is in turn pivoted to the header slide at 53 and is connected to the crankshaft 54 at its opposite end. As the crankshaft 54 rotates about its axis a reciprocating motion is transmitted through the pitman 51 to the header slide 10. It is inherent also that the pitman 51 will oscillate about the pivot 53 and it is this oscillation motion which is utilized to operate the stripper mechanism.

In Figs. 1 and 4 the header slide is shown at its extreme forward position and with the die sleeve 14 abutting against the die block 11 and surrounding the head of the forged blank 56. As the crankshaft continues to rotate about its axis through the arc A to the position shown in Figs. 2 and 5 the header slide moves away from the die block 11 and the pivot 52 moves down in an arc having its center at the pivot 53 due to the previously mentioned oscillating motion of the pitman 51. During the first phase of the stripping operation the entire mechanism moves from the position shown in Figs. 1 and 4 to that shown in Figs. 2 and 5. In Fig. 1 the cam follower 44 is in contact with the cam surface on the levers 34 and 36 at a point 57 and as the crankshaft 54 rotates to the position shown in Fig. 2 the cam follower 44 rolls along the cam surfaces on the levers 34 and 36 until the point of contact 58 is reached. The design of the cam surface and the linkage of the toggle is so arranged that the point of contact between the levers 34 and the stripper operating means and the lever 36 and the punch operating means is in a fixed, axially spaced relationship relative to the die block 11. Since these points on the levers are connected to the punch and the stripper sleeve by the punch sliding members and the stripper sleeve sliding members the punch and the stripper sleeve also maintain their axial space relationship with the die block 11 during this phase of the stripping operation. While this phase of the operation takes place the header slide and the header slide extension move axially away from the die block 11 due to the rotation of the crankshaft. It is during this phase of the operation that the stop engages the radial surface 16 of the header slide extension causing the die sleeve to move axially away from the die block 11. Since the stripper sleeve and punch maintain their relative axial space from the die block thereby holding the blank 56 against motion and since the die sleeve moves axially away from the die block, the blank 56 is effectively ejected from the die sleeve as is shown in Figs. 2 and 5. The cam surfaces on the levers 34 and 36 between the points 57 and 58 may be formed identical to insure that the levers move as a unit thereby preventing any relative motion between the punch and stripper sleeve; however, it is preferable to form the cam surface on the levers 34 between these points with a slight clearance so that no driving engagement is made with the cam followers. By employing this preferred structure, the stripper engages the advance block thereby causing the punch and stripper sleeve to be advanced by the lever 36. This, of course, guarantees that the punch and the stripper sleeve advance as a unit during this phase without any relative movement therebetween.

The second phase of the stripping action takes place as the crankshaft moves from the position shown in Fig. 2 to the position shown in Fig. 3 as shown by the difference between the arc A and the arc B, and it is during this phase of the stripping operation that the punch is withdrawn from the cavity in the blank 56. In the position disclosed in Fig. 2, the end of the first phase and the beginning of the second phase, the plunger block 26 has moved forward relative to the die sleeve 14 until the plunger block face 28 is in engagement with the radial face 29 of the die sleeve 14 thus preventing any more forward travel of the punch relative to the die sleeve. Also, at the point 58 in the cam of lever 36 the cam surface changes so that there is no rotational motion of the lever 36 during the second phase. The cam surface on levers 34, however, continues so that in the second phase of the stripping operation the point of contact between the levers 34 and the series of stripper sleeve sliding members maintain the axial spacing relative to the die block 11 thus retaining the stripper sleeve in a constant axial space relationship with the die block 11. Since the stripper sleeve bears against the blank 56 during the second phase of the operation and prevents the withdrawal of the blank 56 with the punch, the punch is withdrawn from the cavity and the blank 56 completing the stripping operation. The cam follower 44 during the second phase of the stripping operation moves to the point 59 of the cam on the levers 34 and at this point the curve of the cam surface changes so that there is no additional rotation of the levers 34 relative to the header slide 10.

To summarize the stripping operation of this device, it should be noted that during the first phase the cam follower rolls along the cam surfaces of the levers 34 and 36 causing the levers to rotate relative to the header slide 10 in such a way that the stripping sleeve and the piercing pin maintain a constant space relationship with the die block 11 thus holding the blank stationary relative to the die block 11. At the same time, the die sleeve is moved with the header slide 10 and relative to the blank so that the blank is cleared of the die sleeve. During the second phase of the stripping operation the header slide continues to move away from the die block 11 but in this case the punch also moves as a unit with the header slide. Since the action of the cam follower on the cam of the levers 34 causes the stripper sleeve to maintain its space relationship relative to the die block 11, the punch is withdrawn from the cavity in the blank.

During the remaining portion of the complete cycle the blank 56 is ejected from the die block 11 and is transferred to the next operation by any conventional transfer means (not shown). Also, a new blank is inserted or is positioned so that another forging operation may be accomplished.

During the forging motion of the header slide 10 back to the position shown in Fig. 1, the stripper mechanism effectively idles since the cam follower 44 does not maintain contact with the cams formed on the levers 34 and 36 so there is no possibility of unnecessary strain on the stripper mechanism. The entire structure is inherently synchronized so that no exterior means is necessary to synchronize the various operations of the mechanisms.

Having completed a detailed description of a preferred embodiment of the present invention so that others skilled in the art may be able to understand and practice the same, I state that what I desire to secure by Letters Patent is not limited by said preferred embodiment but rather is defined in what is claimed.

What is claimed is:

1. Apparatus for making socket head cap screws comprising a bed frame having a blank holding die, a reciprocating header slide mounted in the bed frame, a shaft mounted in the bed frame for rotation, an eccentric on said shaft, a pitman connecting said eccentric and header slide to reciprocate the header slide, a header slide die slidably mounted on the header slide provided with an opening to surround the head of a blank disposed in said holding die, a stripper sleeve slidably mounted in said header slide die, a punch slidably mounted in said stripper sleeve, means operatively connecting said stripper sleeve, punch and pitman to positively retain said punch and stripper sleeve in a fixed space relationship with said holding die while said header slide moves away from said holding die in response to a portion of the pivotal movement of the pitman with respect to the header slide, and second means operatively connecting said stripper and pitman to retain said stripper in a fixed space relationship with said holding die while said header slide continues to move away from said holding die in response to another portion of the pivotal movement of the pitman with respect to the header slide.

2. In a header having a bed frame with a die block and a header slide reciprocably mounted in said bed frame for advancing and retracting movement with respect to said die block, a die sleeve mounted on said header slide adapted to surround and confine a blank positioned in said die block, a stripper sleeve slidably mounted on said header slide within said die sleeve, a punch slidably mounted in said header slide within said stripper sleeve, means on said header slide to force said punch into the portion of the blank confined within said die sleeve during the advancing movement of the header slide, driving means operating in timed relation to said header slide positively holding said punch and stripper sleeve substantially stationary with respect to said die during the first portion of the retracting movement of said header slide, means on said header slide retracting and stripping said die sleeve from the blank during said first portion of the retracting movement of said header slide, means on said header slide engaging and stripping said punch from the blank during a second portion of the retracting movement of said header slide, and other driving means operating in timed relation to said header slide positively causing said stripper sleeve to lag with respect to said header slide and punch during said second portion of the retracting movement of said header slide.

3. In a header having a bed frame with a die block and a header slide reciprocably mounted in said bed frame for advancing and retracting movement with respect to said die block, a die sleeve mounted on said header slide for limited sliding movement arranged to surround and confine the head of a blank supported in said die block, said die sleeve confining the head of the blank providing a tapered die recess, a stripper sleeve slidably mounted on said header slide within said die sleeve, a punch slidably mounted in said header slide within said. stripper sleeve, means on said header slide to force said. punch into the portion of the blank confined within said die sleeve during the advancing movement of the header slide, driving means operating in timed relation to said header slide positively holding said punch and stripper sleeve substantially stationary with respect to said die block during the first portion of the retracting movement of said header slide, means on said header slide engaging and stripping said die sleeve from the blank during said first portion of retracting movement of said header slide, means on said header slide engaging and stripping said punch from the blank during a second portion of the retracting movement of said header slide, and other driving means operating in timed relation to said header slide positively causing said stripper sleeve to lag with respect to said header slide and punch during said second portion of the retracting movement of said header slide.

References Cited in the file of this patent UNITED STATES PATENTS 2,261,318 Wilcox Nov. 4, 1941 2,271,257 Friedman Jan. 27, 1942 2,583,270 Lynall Jan. 22, 1952 

